The invention relates to a method and a device for error control procedure of an electronic control device of an automatic transmission, especially an automated shift transmission, disposed within the drive train of a motor vehicle.
Automatic transmissions, especially automated shift transmissions, are increasingly used in motor vehicles not just for the sake of driving comfort, but also for the sake of reductions in fuel consumption that can be achieved with them.
FIG. 2 shows a block diagram of a vehicle drive train equipped with an automated shift transmission.
An internal combustion engine 4 is connected via a clutch 6 to a shift transmission 8 from which a drive shaft 10 leads to driven wheels of the motor vehicle.
A power control element 12, for example, a throttle flap in a spark ignition engine or control rod in a diesel engine, that is actuated by an actuator 14 is used to control engine power. An actuator 16 is provided to actuate clutch 6. Actuators, which together are designated as 18, are used to actuate shift transmission 8.
Furthermore, the vehicle has an accelerator pedal 20 and an actuation unit 22 for selecting different gears or shifting programs for the actuation of shift transmission 8.
A transmission control unit 24—which has a microprocessor 26 with program memory 28 and data memory 30 and whose inputs 32 are connected to at least some of sensors 34, 36, 38, 40, 42, 46, 48 and 50 to determine the position of actuation unit 22 of power control element 12, the engine speed, the speed of a transmission input shaft, the speed of the drive shaft, the position of the actuators 18 of transmission 8, the position of accelerator pedal 20 and the position of clutch actuator 16—is used to control actuators 16 and 18.
The transmission control device 24 is connected to an engine control device 52 via a bus 54 whose outputs are connected to actuator 14 as well as a fuel supply system of engine 4 and in some cases an ignition as well as in some cases additional control rods of engine 4 and whose inputs are joined to some of the aforementioned actuators and in some cases additional actuators.
The division of hardware and software scopes may differ between controllers 24 and 52.
Structure and function of the system are known in and of themselves and therefore are not explained in further detail. The shift operations of shift transmission 8, i.e., of clutch actuator 16 and actuators 18 are controlled in particular as a function of the position of accelerator pedal 20 or the position of power control element 12, which may be linked directly with accelerator pedal 20 or actuated completely electronically, and the speed of drive shaft 10 and/or the engine speed, where a complex program stored in program memory 28 of transmission control 24 determines the particular gear to be engaged or the sequence of the shift operations. At least during a shift operation, the torque to be output by the engine is determined not just by the position of accelerator pedal 20, but also by the program controlled via transmission control device 24, because when disengaging clutch 6 for a gear change the engine torque in most cases must first be backed off in order to increase again when engaging the clutch after shifting the gear, so that a comfortable gear change is ensured. The intervention in the engine torque may occur in this case directly through an appropriate electronically controlled actuation of the power control element 12, via an additional power control element 12 or by intervention in the ignition.
If, because of errors in control device 24, a torque is called for by engine 4 that is above the torque desired by a driver, the vehicle, against the wishes of the driver, may accelerate, which leads to safety-critical situations.